DESCRIPTION The applicant has published that T lymphocytes obtained from lungs of smokers demonstrate reduced proliferative responses to agents such as ConA and, when stimulated, fail to produce the usual amounts of IL-2. It is proposed to determine how oxidative stress in the form of H2O2, which has been shown to be generated in tobacco smoke, affects the immunosuppressive properties of hydroquinone and catechol, both of which are present in tobacco smoke. Low levels of H2O2 will be used to determine how it affects the ability of hydroquinone to suppress T cell activation and proliferation. Experiments will be designed to determine to what extent the iron-chelating properties of catechol protects lymphocytes from the inhibitory effects of H2O2. In addition, measurements will be made to determine to what extent conjugates of parabenzoquinone and glutathione correlate with smoke-induced T cell suppression. In addition, quinone-glutathione levels will be determined by HPLC to determine if this is a useful biomarker for suppressed T cell responses.